---
title: swrDelta
description: Set a custom stale-while-revalidate period for ISR enabled pages.
---

{/* The content of this doc is shared between the app and pages router. You can use the `<PagesOnly>Content</PagesOnly>` component to add content that is specific to the Pages Router. Any shared content should not be wrapped in a component. */}

You can specify a custom stale-while-revalidate period for CDNs to consume in the `Cache-Control` header for ISR enabled pages.

Open `next.config.js` and add the `swrDelta` config:

```js filename="next.config.js"
module.exports = {
  // one year in seconds
  swrDelta: 31536000,
}
```

Now instead of an empty `stale-while-revalidate` period being provided in the `Cache-Control` header, the custom period will be included.
